19 



The original substance to wMcli the name zinc bloom or zinc bliithe 

 was given, and which consists of a species of efflorescence which forms 

 on the walls of zinc mines, and upon the rubbish taken out of the work- 

 ings, appears to be a different compound from that which we have been 

 describing. Smithson first, I believe, analysed a specimen of this 

 mineral in small mammiform patches from Bleiberg, in Carinthia. Ano- 

 ther analysis of it was made by Dr. Carl Schnabel,*' with a specimen 

 which had effloresced upon the rubbish at Ramsbeck, in "Westphalia, 

 under the influence of strong sunshine. Similar efflorescences are found 

 upon a curious blende, which occurs in globular and reniform masses, 

 formed of concentric layers at the Yenta, near Comillas, specimens of 

 which we have analysed; and also upon some Smithsonite from the mines 

 of Florida. These different specimens agree very well in composition, 

 and may be represented by the formula 3ZNO,C02,3E[0. The white 

 compound which forms upon the surface of metallic zinc when moist- 

 ened, and exposed to the air, appears to belong to the same category, as 

 the following table, containing the results of all the analyses, shows : — 



rfllmilfltPnl VPTita Bleiberg Eamsbeck.t Artificial Compound 



Calculated. Yenta. (Smithson). (Schnabel). (Bonsdorff). 



3ZnO, . 71-311 .... 71-260 . . 71-4 . . . 71-210 .... 71-25 



99-998 100-000 100-0 100.000 100-00 



In this formula the sum of the equivalents of carbonic acid and water 

 exceed the number of equivalents of oxide of zinc, and consequently 

 the objections urged against Schindler's formula apply here with equal 

 force. We had not, however, enough of the mineral to determine the car- 

 bonic acid separately, or whether a portion of the water could be driven 

 off at a lower temperature than the rest. It would be useless to 

 discuss the matter further until the whole of the compounds of oxide of 

 zinc with carbonic acid and water, obtained by precipitating salts of 

 zinc by means of carbonates, by the rusting of zinc, &c., shall be re- 

 examined. It is interesting, however, to find that the natural com- 

 pounds obtained by precipitation and by efflorescence, exhibit exactly 

 the same diff'erence as the artificial ones, and, furthermore, that the cor- 

 responding natural and artificial bodies are identical in composition. 



Messrs. Petersen and Yeit give 3*52 as the specific gravity of the 

 Spanish hydrocarbonate of zinc ; while M. Terrell gives 2-042. The fol- 

 lowing observations will, we think, explain the discrepancy. A piece 

 of 'No. I., when allowed to absorb water completely, was found to have 

 the density 3-758 ; the quantity of water absorbed was 18-189 per cent. 

 If we consider that before absorbing this quantity of water it had first 

 displaced it, the specific gravity of the mineral, supposing it to have 



Pogg. Annal. cv. 144. 



t We have deducted the foreign matters and hygroscopic water, and reduced the 

 ^esidue to the standard of 100 parts. 



